The present invention relates to an electrothermal drying device. More particularly, the present invention relates to an electrothermal drying device which can dry an insulation sheet continuously after the insulation sheet is dipped in a polymer-impregnated resin solution.
An insulation sheet for a printed circuit board has one or more layers of carbon fiber fabric sheet or glass cloth sheet. The insulation sheet is dipped in a polymer-impregnated resin solution. The resin is a thermosetting resin such as an epoxy resin, a polyimide resin, a polyester resin, or a phenolic resin. After the insulation sheet is dipped in a polymer-impregnated resin solution, the insulation sheet is dried by a drying device. The function of the insulation sheet is to support a copper cladding in a printed circuit board. Referring to FIG. 1, a conventional drying device comprises a hollow main body 1 which has a drying chamber A, a plurality of hot air nozzles 2, and a plurality of air-inhaling channels 3, 3a. The hollow main body 1 is made of metal plates and heat-preserving plates. The conventional drying device can dry an insulation sheet after the insulation sheet is dipped in a polymer-impregnated resin solution 27 and carried by a plurality of rollers 26 to form a polymer-impregnated insulation sheet 4. The hot air passes through the hot air nozzle 2 to heat the polymer-impregnated insulation sheet 4 while the polymer-impregnated insulation sheet 4 is transported through the hollow main body 1. The solvent of the polymer-impregnated resin solution becomes vapors L which are exhaled by a blower. The hot air nozzle 2 has a large number of vent holes in order to stabilize the hot air. However, turbulent flow may occur so that the drying period in different drying sectional areas may vary. The dust may adhere to the surface of the polymer-impregnated insulation sheet 4. Furthermore, the hollow main body 1 is large and the air filtration effect is poor.
Referring to FIG. 2, another conventional drying device comprises a hollow main body 32 having a drying chamber H, a plurality of electrothermal radiation plates 33, a plurality of anti-knocking wires 34 connected to two controllers 35, and four hot air circulation devices 36. The drying device can dry an insulation sheet after the insulation sheet is dipped. in a polymer-impregnated resin solution 27 and carried by a plurality of rollers 26 to form a polymer-impregnated insulation sheet 4. The electrothermal radiation plates 33 can produce infrared radiation energy to heat the polymer-impregnated insulation sheet 4 while the polymer-impregnated insulation sheet 4 is transported through the hollow main body 32. The hot air O enters the hot air circulation system. The solvent of the polymer-impregnated resin solution becomes vapors P to be exhaled. When the polymer-impregnated insulation sheet 4 is broken in the hollow main body 32, the broken portion of the polymer-impregnated insulation sheet 4 may ignite on touching the electrothermal radiation plates 33. Therefore, it is very dangerous to use the conventional drying device.